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Tower Bridge: An Icon of London

Intro

With the mighty river Thames snaking through it, London has many iconic buildings, some of which cross the river itself. None of these bridges are more eye-catching than Tower Bridge. With its ability to open up to let passing ships through, its technologies were beyond ambitious for their time and are still used to this day.

This icon of Victorian engineering, sits next to the medieval castle of the Tower of London and the futuristic glass ‘motorcycle helmet’ of the Mayor’s office. Three eras of the city’s history are encapsulated in this one area. This is Tower Bridge.

The Need

At the end of the 19th century, commercial development in the East End of London had increased. There was demand from traders and the public for a new river crossing downstream from London Bridge.

The traffic situation on London bridge had become so bad, that during a 2-day survey conducted in August 1882, it was found that London Bridge’s traffic was 22,242 vehicles and 110,525 pedestrians in a 24-hour period. With the population of London at the time being nearly 5 million people, this amount of congestion in one area was unstainable and threatened trade in the newly developed East End.

To alleviate this congestion, options were looked at such as widening London Bridge but this was seen as too costly and would cause further disruption. Finally, it was decided that a new bridge would be needed closer to the East End of London.

However, building a new bridge would be difficult. A traditional fixed bridge at street level would not be viable due to the disruption of river traffic, effectively cutting off access by sailing ships to the port facilities in the Pool of London, a stretch of water between London Bridge and the Tower of London.

With this huge challenge laid out in front of them, the City of London Corporation, the metropolitan governing body of the City of London, formed in 1876 the Special Bridge or Subway Committee to generate ideas. They thought the best course of action would be to hold a competition to see if anyone had a workable solution to their bridge problem.

Designing the Seesaw

The committee, chaired by Sir Albert Joseph Altman, had over 50 entries submitted. One of these was from civil engineer Sir Joseph Bazalgette, whose CV included designing London’s sewage system. However, his bridge design was rejected because of a lack of sufficient headroom for passing ships.

Other designs included were; low-level bridges which would have blocked the trade ships from passing underneath, Duplex bridges with a lock gate system allowing for road and river access simultaneously, also there were bridges with a rolling road, opening to let ships through.

After many rejections, a design was finally approved in 1884. The design by architect Sir Horace Jones, who also happened to be one of the competition’s judges, opted for a bascule bridge, which comes from the French word for a seesaw.

Essentially, a bascule bridge is a type of drawbridge, which works on a pivot with a heavy weight at one end to balance the length at the other end. The architects and engineers agreed the bascule design was the most viable, causing the least disruption to pedestrians and road traffic. Consisting of two

piers and a central opening span, once raised it would allow for river traffic to pass through, while high-level walkways would provide continued access to pedestrians.

The design may have been approved but it looked slightly different to how the bridge does today.

Boasting a big arch where the high-level walkways are now located. The design needed some refinement so it could serve both pedestrians and river traffic before construction could begin.

Planning the Bascule

Sir John Wolfe Barry was appointed engineer serving with architect, Sir Horace Jones. Barry also appointed his friend, Henry Marc Brunel as assistant engineer. That surname may sound familiar. Henry was the son of Isambard Kingdom Brunel, who knew a thing or two about bridges himself.

Sidenote here, the engineer of Tower bridge was the youngest son of Sir Charles Barry, who designed the Houses of Parliament.

In November 1885, the design of Tower Bridge was finalised and a Bill was presented to the UK Parliament to allow construction to begin.

The Bill contained many elements; from the size of the bridge, its location and who would be responsible for its operation. It specified that the opening span of the bridge would provide a clear width of 200 feet that’s 61 metres and headroom of 135 feet or 41 metres when the bridge was opened. However,

once construction began these measurements were exceeded by 5 feet or 1.5 metres and 6 inches/ 15 centimetres respectively.

The site chosen for Tower Bridge, just north of the Tower of London, is in an area surrounded by wharves, the areas where ships could be moored to load and unload. This location was chosen due to the access to the pool of London, this area has been used since Roman times for ships carrying goods to be loaded and unloaded.

As for the design of Tower Bridge, the Bill stated that the design had to be in a style in keeping with Victorian London, a Gothic-style similar to the Houses of Parliament. Whilst the brickwork would maintain visual continuity with the Tower of London.

Other parts of the Bill, concerned the running of the bridge and contingencies if the bridge failed. One way of alleviating danger from the river traffic was, that a tug boat should be stationed at the bridge at all times to assist any vessels in danger when crossing the bridge. This requirement stayed in place until the 1960s.

Once the bill was passed, and the Tower Bridge Act signed into law, it regulated the bridges use, something which it still does to this day.

Construction of Tower Bridge began in 1886, with the first job laying the foundations of the piers.

Sinking the Foundations

Before work could commence on the building of the Tower Bridge, the area the bridge was to cross had to be surveyed, levelled and prepared. This process involved the lowering of large metal cages called caissons. These were

lowered into where the piers would be built in the Thames. The caissons created a barrier between the river and the worksite.

Once the caissons were in place, divers would work within them. It was a time-consuming process of excavating the clay, mud and gravel that made up the riverbed. Much of this was done by shovelling the exhumed material onto a crane that hoisted the removed material onshore.

As the excavating progressed over the next 3 years, the caissons sank inch by inch into the clay under their own weight. When they had reached a depth of 19.6 feet or 6 metres, the water in the caissons could be pumped out and work on the piers could begin.

Due to the skill required to set the foundations and the prestige of the project only the best would do. 6 of the best divers of the time were employed, led by Quaker, Friend Samuel Penney who specified that he had his own daughter operate the air pump for him during his excavation of the foundations because he trusted no one else to do so.

The other divers were; John William Bateman, Thomas Clucas, Stephen Nott Fry, James Rouse and James Thacker who are now memorialised by a bronze plaque inside the North Tower of the Bridge.

Construction

Over the course of the next 8 years, construction took place on Tower Bridge. 432 workers were employed over this period. Most of these workers came from Scotland.

Despite being over 300 miles/ 482 kilometres away, the 11,000-ton steel skeleton forming the main structure of the bridge was constructed by the Scottish civil engineering company Sir William Arrol & Co. Based in Glasgow.

This company had built some of the UK’s most famous bridges, including the Forth Bridge and Tay Rail Bridge.

Picture of the Tower Bridge Piers being built

Skilled, experienced labour was essential in such a project. It was essential that no expense was spared when it came to the labour.

It’s because of the high number of experienced bridge builders working on Tower Bridge, that has been credited for the reason so few injuries took place during construction. However, building such a project didn’t come risk-free, with 10 workers losing their lives during building. Nevertheless, this is still a low number considering the timeframe and number of workers involved.

Maintaining the look

The 11,000 tons of steel framework of Tower Bridge, maybe remarkable but most of it is hidden beneath the iconic stonework. Made from 235,000 cubic feet of Cornish granite and Portland stone and backed with traditional brickwork. A staggering, 31 million bricks make up Tower Bridge – this

masonry was used specifically to complement the Tower of London just north of the bridge.

But, not all that steel was covered. Besides the towers of the bridge is the striking steel suspension, with an estimated three million rivet holes drilled into it to keep the bridge held up and anchor the bridge to banks for the bascules to work.

Tower Bridge doesn’t just rely on its deep foundations and steel frame to stay upright, but it is part suspension bridge. These thick chains also help keep the bridge upright and take the strain off when it is raised for passing ships.

Originally painted chocolate brown, not the most desirable colour but one which fitted its surroundings at the time. It has received several paint jobs over the years. Notable times were, during the Queen’s silver jubilee, when it was painted red, white and blue. Now it sports a more vibrant blue and white colour scheme.

Splitting the Road

As I have said, the bascule design allowed ships to pass through by allowing the bridge to split into two. To attain this the bridge needed some big engines and ideas of the Victorian era. Sir William Armstrong had the solution with his new invention, the hydraulic accumulator.

But before we go into the complexities of the accumulator, the hydraulics needed powering, and this being the Victorian period there was only one readily available option.

In keeping with the rest of the industrial revolution, it was steam power. The energy of choice during most of the 1800s. The London Hydraulic Power Company powered much of London including; cranes, lifts, workshops, theatre machinery, and was the company that provided power and workers for the bridge.

Three large boilers housed within the towers generated the power for the lifting mechanism. These boilers were continuously fuelled by stokers working in 24 hours shifts to ensure there was enough energy available to lift the bridge whenever required. At its peak use, Tower Bridge was opened 20-30 times a week!

With that amount of demand, required a staggering 20 tons of coal a week to fuel the fires and the steam to power the large steam pumping engines in the engine room.

Resembling a steam train with its bright green and red colour scheme and ran like one while in motion. The engine’s pistons turned a large flywheel at the same time as powering a set of hydraulic pumps, which pushes water into six huge storage containers of the hydraulic accumulators.

Acting like batteries, storing up the energy by holding the water under high pressure, allowing for users to store potential energy and access it when required. In turn, this meant that power was always readily available.

When Tower Bridge was required to open, the water was released into the drive engines, powering yet more pistons to turn a set of cogs. These cogs connect to a rack on the back of the bascules, opening them for passing river vessels.

Despite the complexity of the system, the bascules only take about a minute to raise to their maximum angle of 86 degrees.

Today, the bascules are still operated by hydraulic power, but since 1976 they have been driven by oil and electricity rather than steam.

The original pumping engines, accumulators and boilers are still in the towers but merely as display pieces in the engine rooms.

A consideration for pedestrians was also built into the towers of the bridge. Walkways across the bridge were open to the public but were closed in 1910

due to lack of use. Another contributing factor was, that of their relative obscurity made the walkways a place for muggings and assaults to take place.

Now, the walkways are part of the Tower Bridge Exhibition, and as of 1982, were fitted with glass floors for visitors to enjoy the views below them.

With the building complete and once the engines were fitted and tested, it was now time for the bridge to open up.

Opening Up

On the 30th June 1894 and after a total cost of £1,184,000 the equivalent of £136 million today, Tower Bridge was finally opened by Prince Edward of Wales and Princess Alexandra of Wales, in a grand celebration. Also in attendance were the Lord Chamberlain, Lord Carrington and the Home Secretary, H. H. Asquith.

But, not in attendance was the original architect, Horace Jones. He died a year into construction and never got to see his bridge, the momentous achievement in civil engineering and architectural design in all its glory. Upon its completion, the bridge was considered the largest and most sophisticated bascule bridge ever made.

You may presume that there is some sort of toll for opening the bridge, but there isn’t. As par, the act of Parliament, passing through Tower Bridge is toll-free. Also, there is 24 hours notice given before the bridge is raised.

Although Tower Bridge is undoubtedly a landmark, it hasn’t always been seen as one. In the early 20th century several people were critical of its aesthetics. With architect Henry Heathcote Statham writing; “It represents the vice of tawdriness and pretentiousness, and of falsification of the actual facts of the structure”. Roughly translating, I don’t like how it looks and I think it’s over-engineered.

Another criticism came from Welsh artist Frank Brangwyn stating that; “A more absurd structure than the Tower Bridge was never thrown across a strategic river”. Sick burn there.

Jumping the Gap

There haven’t always been smooth crossings over the bridge. It had been repeatedly targeted by German bombers during the Second World War. Sustaining damage to its walkways, bascules and knocking out the engine room. A third engine was installed after this as a backup but became redundant when the system was modernised in 1974.

Although it had survived bombings and eccentric pilots repeatedly flying planes through its towers over the years. One of these was Frank Miller, who in 1951, flew his plane through Tower Bridge. Although he was not the first to do this, his excuse was somewhat bewildering.

Miller blamed it on his 13-year-old son, saying that he had dared him to do it for 35 shillings that’s around £30 in today’s money. Unfortunately for Frank, this did not cover the £100 fine he got in court.

However, the next year would see one of the most infamous incidents in the history of the bridge occur.

On 30th December 1952, bus driver Albert Gunter was happily driving his number 78 red double-decker bus, on his usual route across Tower Bridge. As he was making the crossing heading south, something unexpected occurred. The road appeared to be moving up in from him. The bridge was opening.

The usual process would have the gateman ring the warning bell and close the gates when the bridge was clear before the watchman ordered the raising of the bridge. This process failed while a relief watchman was on duty. As the bus was nearing the edge of the south bascule, it started to rise. Albert made a split-second decision and slammed his foot on the accelerator.

The diesel engine roared and the bus made a daredevil jump across. The clearing was a mere 3-feet/0.91 metre gap but the drop to the other bascule was 6 feet or 1.8 metres onto the north bascule, which had not yet started to rise.  

Landing with a thud the bus was intact and all 20 of the passengers on board were safely across. As a precaution, all of them were taken to hospital. There were no serious injuries, however, there was one injury. Poor Albert had broken his leg.  

Albert Gunter was given £10 equivalent to £290 in 2019 by the City of London Corporation to honour his act of bravery and a day off work.  

A less dramatic incident happened in May 1997. During the presidential visit of U.S. President Bill Clinton, his motorcade was divided up by the opening of the bridge. The Thames sailing barge Gladys, on her way to a gathering at St Katharine Docks, arrived on schedule and the bridge was opened for her. 

Returning from a Thames-side lunch at Le Pont de la Tour restaurant with UK Prime Minister Tony Blair, President Clinton was less punctual and arrived just as the bridge was rising. The bridge opening split the motorcade in two, much to the consternation of the security staff. A spokesman for Tower Bridge is quoted as saying: “We tried to contact the American Embassy, but they wouldn’t answer the phone.”  

An Icon of London   

Throughout its history, Tower Bridge has become an icon of London. A staple in an ever-changing skyscape of a city constantly under construction.  

Making many appearances in films and television shows. Whenever there is a drone shot of London, one of the images that tell you what city you’re looking at is Tower Bridge.  

In recent memory, Tower Bridge was a focal point for the 2012 London Olympics. With the Olympics rings suspended from the towers. It was also involved with the opening ceremony.  

Furthermore, the bridge has inspired architects around the world. In fact, in the Chinese city of Suzhou, there stands a replica of Tower Bridge. With 4 towers, instead of London’s 2 and this is just a standard bridge. Without the bascules opening and closing for river traffic. 

The bridge can still make headlines as well. In August 2021, Tower Bridge’s bascules got stuck open and the fault was not able to be fixed for up to 12 hours, bringing considerable traffic chaos to that part of the city.  

Even part of a myth, there is a tale of Tower Bridge being bought by an American tycoon, who thought he was buying Tower Bridge but in fact bought London Bridge. And, of course, this just isn’t true.  

Through its 127-year history, it is still used as a vital crossing point for the people in London. With the many great minds of the Victorian age coming together to produce an engineering marvel that has stood the test of time. 

Revered in its time and now a symbol of London, this is more than just a bridge, it is now a piece of history. 

Sources: 

https://www.bbc.co.uk/news/uk-england-london-58149716

https://h2g2.com/edited_entry/A559

https://en.wikipedia.org/wiki/Tower_Bridge

https://www.towerbridge.org.uk/discover/history

https://wondersofworldengineering.com/tower-bridge.html

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